1,720,964 research outputs found
On the Performance Improvement of a Cellular Network Supported by an Unmanned Aerial Base Station
No full textThis paper studies a cellular network, where base stations move according to traffic/service needs; cov- erage and capacity offered are adaptive to the time-spatial variations of user demand. In particular, we analyze the performance of a network, where a base station is carried by a UAV (Unmanned Aerial Vehicle, sometimes also denoted as drone). The Unmanned Aerial Base Station (UABS) flies over an urban area, offering coverage and capacity to users that are not served by the Terrestrial Base Stations (TBSs); in our scenario we consider in particular video users with stringent requirements in terms of downlink throughput. The paper proposes an approach to design the trajectory of the drone, that accounts for the actual position of users that are unsatisfied by the TBSs. The approach is based on the identification of clusters made of nearby users to be served, and a simple Nearest Neighbor algorithm. The potential improvements in terms of network capacity (sum throughput) and user satisfaction are estimated, in a scenario where the UABS uses a separate band with respect to the TBSs. This performance increase can be seen as an upper bound to the improvements that would be achieved by using the same band, where the UABS would actually interfere with the TBSs
QoE and cost-aware resource and interference management in aerial-terrestrial networks for vehicular applications
No full textAbstract—In this paper, we address the deployment of Unmanned Aerial Vehicles (UAVs) as Unmanned Aerial Base Stations (UABSs) which cooperate with Macro Base Stations (MBSs) in an urban environment to serve vehicles, denoted as Ground User Equipments (GUEs), implementing vehicle-to-everything (V2X) services. As vehicles perform extended sensing, exchanging data with nearby GUEs through UAVs and MBSs links, we propose an Integer Linear Programming (ILP) model that jointly optimizes radio resources allocation and beamforming, while accounting for vehicular application requirements, backhaul capacity limits and interference between GUE-UABS and GUEMBS links. The model allows also to find a trade-off between benefits and cost of UABSs activation. Two system architectures are considered: a distributed model, where MBSs independently run the Radio Resource Management (RRM) algorithm sharing information with each other, and a centralized model, where MBSs send information to the network core, where the optimization algorithm runs. The study investigates interference through two resource allocation approaches, considering splitting and sharing of resources among UABSs and MBSs. Numerical evaluations demonstrate the effectiveness of using UABSs to improve the Quality of Experience (QoE) of GUEs. We also compare the two architectures, considering both resource pool assignments, and highlighting the impact of varying UABSs parameters and activation costs
Optimizing beam selection and resource allocation in UAV-aided vehicular networks
No full textFuture mobile radio networks require a degree of flexibility that technologies like Unmanned Aerial Vehicles (UAVs) carrying Base Stations (BSs) can provide. It is expected that the lower space above cities will be populated by many different types of UAVs, such as taxis and smaller drones used for logistics or patrolling, which can be equipped with BSs to serve users on the ground, while flying for their given mission. We investigate an urban scenario with terrestrial macro BSs (MBSs) deployed, where multiple UAVs are flying on a given path. Vehicles in the area are moving while relying on network services, and MBSs alone might not serve them adequately. UAVs operate as BSs, helping the MBSs. Vehicles are assumed to be satisfied if an appropriate quality of experience (QoE) is fulfilled, that is they are able to upload a given amount of data during a given time window, continuously. We assume BSs use beamforming and a limited number of beams can be activated at the same time on UAVs. This paper proposes an optimization algorithm allowing to select the best set of beams to be activated at each UAV and the best set of resource units per vehicle, in order to maximaze the QoE. The algorithm jointly considers: i) resource management at both MBSs and UAVs; ii) traffic prioritization to attain the continuous service; iii) a limited backhaul capacity. Numerical results show the notable improvement of satisfied users when the flying BSs are present and report the impact of backhaul capacity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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